Use of chènevotte, a valuable co-product of industrial hemp fiber, as adsorbent for copper ions: Kinetic studies and modeling

In this study, a series of hemp shives (chènevotte) with different chemical compositions and properties, namely a raw (SHI-R), a washed with water (SHI-W), three samples chemically modified with KOH (SHI-OH), Na2CO3 (SHI-C) or H3PO4 (SHI-H), and a hemp shives sample prepared by grafting of carboxylic groups (SHI-BTCA), were used as adsorbents for the removal of copper present in aqueous solutions. This article presents the abatements and kinetics obtained using batch experiments and their modeling. The results first showed that the quantity of copper removed depended on the used shives and the copper initial concentration. At the same experimental conditions, SHI-C and SHI-BTCA samples possessed similar performances which are significantly higher than those of other studied hemp shives. Copper adsorption reached equilibrium after 60 min of contact time and was independent of concentration in the range 5–150 mg/L for SHI-C and SHI-BTCA. According to the better Chi-squared values, the experimental data were better simulated by the non-linear kinetic model in the order: Lagergren < Elovich < Ho and McKay < Weber and Morris < Boyd for SHI-C and Boyd < Ho and McKay < Weber and Morris < Lagergren < Elovich for SHI-BTCA. The analysis of data indicated that chemisorption is the main mechanism for binding copper onto SHI-BTCA, while physisorption (diffusion) is the main interaction for copper adsorption onto SHI-C. The adsorption-oriented process using hemp shives could be an advantageous approach for recovering copper from metal industry effluents due to the simplicity of the process, its efficiency to treat both diluted and concentrated copper solutions, and the low-cost, non-toxic to humans and the environment, ecological character, and facile use of hemp shives.